Microbiology CH 3 & 4

What four structures do all bacteria possess?

• Plasma membrane

• Cytoplasm

• Ribosomes (70S)

• Nucleoid (DNA)

Name three structures only some bacteria possess.

• Flagella

• Capsule (glycocalyx)

• Pili/Fimbriae

What is a coccus?

Spherical (round)

What is a bacillus?

Rod-shaped

What is a spirillum/spirochete?

Spiral-shaped

What does diplo- mean?

Pairs

What does strepto- mean?

Chains

What does staphylo- mean?

Clusters

What are the functions of the bacterial plasma membrane?

• Selective barrier

• Nutrient transport

• ATP production

• Waste removal

What is peptidoglycan?

A strong mesh-like material that gives bacteria shape and protection.

Gram-positive bacteria have ______ peptidoglycan.

Thick

Gram-negative bacteria have ______ peptidoglycan.

Thin

Which bacteria stain purple?

Gram-positive

Which bacteria stain pink?

Gram-negative

Why are Gram-positive bacteria stronger?

Thick peptidoglycan layer provides more strength.

Which bacteria contain LPS (lipopolysaccharide)?

Gram-negative bacteria

What is endotoxin?

LPS that can cause fever, inflammation, and septic shock.

What makes bacteria acid-fast?

Mycolic acid (waxy cell wall)

Name two acid-fast genera.

• Mycobacterium

• Nocardia

Why is the acid-fast stain useful?

Identifies bacteria with waxy cell walls that Gram stain poorly.

Why is tuberculosis treated for at least six months?

Mycolic acid makes antibiotics penetrate slowly.

Mycobacterium vs. Mycoplasma

Both can infect humans.

• Mycobacterium has a waxy cell wall.

• Mycoplasma has no cell wall.

What is passive transport?

Movement without energy.

What is active transport?

Movement requiring ATP.

What is diffusion?

High concentration → low concentration.

What is facilitated diffusion?

Diffusion using transport proteins.

What is osmosis?

Movement of water across a membrane.

Hypertonic solution?

Water leaves the cell → cell shrinks.

Hypotonic solution?

Water enters the cell → cell swells.

Isotonic solution?

No net water movement.

Function of flagella?

MOVEMENT

Function of fimbriae?

Attachment

Function of conjugation pilus?

Transfers DNA between bacteria.

Capsule vs slime layer?

• Capsule = organized, firmly attached

• Slime layer = loose, easily removed

Function of capsule?

• Prevents phagocytosis

• Helps bacteria stick to surfaces

What is the nucleoid?

Region containing bacterial chromosome.

Function of cytoskeleton?

: Maintains shape and assists cell division.

Function of 70S ribosomes?

Protein synthesis.

Why are bacterial ribosomes medically important?

Antibiotics target 70S ribosomes without harming human 80S ribosomes.

What is an endospore?

Dormant survival structure.

What is inside an endospore?

A:

• DNA

• Cytoplasm

• 70S ribosomes

• Cell membrane

• Cell wall

Why are endospores dangerous?

Extremely resistant to heat, drying, chemicals, and disinfectants.

• EX:Clostridium difficile (C. diff)

What precautions are used with C. diff?

Contact precautions (gown and gloves).

What defines a bacterial species?

Group of bacteria with similar DNA and characteristics

What does the endosymbiotic theory state?

Mitochondria and chloroplasts evolved from bacteria that lived inside another cell.

• Own DNA

• 70S ribosomes

• Divide by binary fission

• Double membrane

Animalia

Multicellular, no cell wall

Plantae

Multicellular, cellulose cell wall

Fungi

Uni- or multicellular, chitin cell wall

Protista

Mostly unicellular

General life cycle, Helminths

Egg → Larva → Adult worm

Tapeworm transmission

Eating contaminated food.

Pinworm transmission?

Ingesting eggs.

Prevention?

A:

• Hand washing

• Cleaning surfaces

• Cooking food

Function of fungal spores?

Reproduction

Function of bacterial endospores?

Survival

What is mycosis?

Fungal infection.

Superficial mycoses?

A:

• Candida

• Trichophyton (ringworm)

Systemic mycosis

Candida

Where are protozoa commonly found?

Water and moist environments.

Giardia transmission?

Contaminated water.

Cryptosporidium transmission?

Contaminated water.

Brain-eating amoeba transmission?

Water enters nose while swimming.

oxoplasmosis transmission?

Cat litter.

Malaria transmission?

Mosquito bite.

Animal membrane contains?

Cholesterol

Fungal membrane contains?

Ergosterol

Plant cell wall?

Cellulose

Fungal cell wall

Chitin

80S ribosomes function?

Protein synthesis.

Nucleus function

Stores DNA.

Rough ER

Makes proteins

Smooth ER

Makes lipids

Golgi apparatus?

Modifies and packages proteins.

Vesicles

Transport materials.

Mitochondria function?

ATP production.

Prokaryotes vs Eukaryotes

A:

• Prokaryotes: No nucleus, no membrane-bound organelles, 70S ribosomes, binary fission

• Eukaryotes: Nucleus, membrane-bound organelles, 80S ribosomes, mitosis/meiosis

Gram+ vs Gram-

• Gram+: Thick peptidoglycan, purple

• Gram-: Thin peptidoglycan, outer membrane with LPS, pink

Endospore vs Fungal Spore

A:

• Endospore = survival

• Fungal spore = reproduction

Bacteria vs Archaea

• Bacteria have peptidoglycan.

• Archaea lack peptidoglycan and often live in extreme environments.

70S vs 80S ribosomes

• 70S = bacteria (also mitochondria and chloroplasts)

• 80S = human/eukaryotic cells

Gram Stain Steps

1. Crystal violet (purple)

2. Iodine (mordant)

3. Alcohol/acetone (decolorizer)

4. Safranin (pink counterstain)

Results:

• Gram-positive = Purple

• Gram-negative = Pink

How can antibiotics kill bacteria without harming humans?

• Target the peptidoglycan cell wall, which human cells do not have.

• Target 70S ribosomes, since human cells have 80S ribosomes.